1. Field of the Invention
The present invention relates to an exposure apparatus and a method of manufacturing a device using the same.
2. Description of the Related Art
A scanning exposure apparatus which exposes a wafer to light while scanning a reticle and the wafer relative to an optical system is the current mainstream exposure apparatus serving as an apparatus for manufacturing a semiconductor device. To scan the reticle and wafer, a configuration including a reticle stage and wafer stage fixed on the same structural member has been proposed. The reticle and wafer are moved at a high acceleration by generating a force using a driver provided to each stage. A driving reaction force generated during the movement at a high acceleration acts on the structural member, and vibrates it. The structural member supports a reference plate on which a projection optical system is mounted through an anti-vibration apparatus, and its vibration leads to vibration of the reference plate and projection optical system and degrades the overlay accuracy in the exposure apparatus.
Hence, to minimize the driving reaction force transmitted from each stage to the structural member in the exposure apparatus, a technique associated with a counter mass mechanism which uses the law of conservation of momentum is often adopted, as described in Japanese Patent Laid-Open No. 2002-208562. The counter mass mechanism includes a counter mass stage which passively moves in the direction opposite to that in which the reticle stage or wafer stage moves, and makes ideally no driving force be transmitted from either of these stages to the structural member.
The counter mass mechanism will be described with reference to FIG. 3. A structural member 107 is supported on the floor through spring elements such as leveling blocks 124. The structural member 107 vertically supports a positioning stage 101 and a counter mass stage 103 using guides 151 such as static pressure bearings so that their horizontal friction can be ignored. A stage driver 115 which generates a force between the positioning stage 101 and the counter mass stage 103 is placed between them. The force generated by the stage driver 115 horizontally moves and positions the positioning stage 101. In this example, the positioning stage 101 and counter mass stage 103 have the same mass m. The center of gravity positions of the positioning stage 101 and counter mass stage 103, and the positions of the points of action of forces F generated by the stage driver 115 are aligned on one straight line in the moving direction. Also, to prevent the counter mass stage 103 from considerably deviating from an assumed position upon a tilt of the structural member 107, a counter mass driver 105 which generates a force between the counter mass stage 103 and the structural member 107 is placed between them. Ideally, there is no need to generate a force using the counter mass driver 105, and the position of the counter mass stage 103 is corrected by generating a force at an appropriate timing only when, for example, the counter mass stage 103 considerably deviates from a desired position.
In such a counter mass mechanism, when the stage driver 115 generates forces F, the counter mass stage 103 moves in the direction opposite to that in which the positioning stage 101 moves. Because the two stages have the same mass, they move at the same speed by the same distance. At this time, no disturbance forces due to the forces F generated by the stage driver 115 are input to the structural member 107, so the structural member 107 does not vibrate. Also, Japanese Patent Laid-Open No. 2005-109441 discloses a technique of providing a driver in a portion which supports the structural member so as to cancel disturbance forces input to the structural member.
Upon adopting an ideal counter mass mechanism, no disturbance forces are generated in the structural member 107 which supports the two stages 101 and 103, due to their driving reaction forces. However, an ideal counter mass mechanism often cannot be implemented due, for example, to design limits or processing variations, and this generates disturbance forces in the structural member 107 and vibrates the structural member 107.
The reason why the structural member 107 vibrates despite the adoption of a counter mass mechanism will be explained with reference to FIG. 4. FIG. 4 shows the same configuration as in FIG. 3 except that in the former the center of gravity positions of the positioning stage 101 and counter mass stage 103, and the positions of the points of action of forces F generated by the stage driver 115 are not aligned on one straight line in the moving direction. In this case as well, when the stage driver 115 generates forces F, the positioning stage 101 and counter mass stage 103 move in the opposite directions, so the forces generated by the stage driver 115 are not directly input to the structural member 107. However, the center of gravity position of the counter mass stage 103 deviates from the vertical positions of the points of action of the forces generated by the stage driver 115. Hence, a moment force M having an amount of deviation L as its arm length is generated in the counter mass stage 103 due to the forces F. The moment force M is transmitted to the structural member 107 through the guides 151 and vibrates it in the rotation direction.
This means that to prevent generation of forces input from the stage driver 115 to the structural member 107, it is necessary to vertically match the center of gravity position of each stage with the positions of the points of action of the forces. However, the center of gravity positions and the points of actions often deviate from each other on the order of several millimeters due, for example, to design limits or variations among components. As the performance specifications of an exposure apparatus become stricter, it becomes harder in practice to make vibration of the structural member 107 fall within a tolerance even when a moment force is generated due to a deviation on the order of several millimeters upon generation of a force of 1,000 N or more by the stage driver 115. Under the circumstances, various approaches are made to improve the design or reduce processing variations so as to implement a counter mass mechanism closer to an ideal one. On the other hand, it is desired to suppress vibration of the structural member 107 by canceling disturbance forces generated in the structural member 107 which supports the two stages 101 and 103.
Further, various disturbance forces other than those due to factors associated with the configuration of the counter mass mechanism are assumed to be generated in the structural member on the exposure apparatus. Examples of the assumed disturbance forces include a disturbance force generated by mounted components connected to each stage with stage movement, that due to factors associated with various drivers placed on the structural member, and that due, for example, to floor vibration, and a vibration suppression system which damps these disturbance forces is required. As a method of canceling disturbance forces input to the structural member 107 which supports the stages 101 and 105, a configuration including a dedicated driver has been proposed but poses problems resulting from the installation space and cost of the driver, as disclosed in Japanese Patent Laid-Open No. 2005-109441.